hydrogen [4-[4-(diethylamino)-alpha-(3,7-disulphonato-1-naphthyl)benzylidene]cyclohexa-2,5-dien-1-ylidene]diethylammonium, ammonium salt

N-[4-[[4-(Diethylamino)phenyl](3-sulfonato-7-ammoniooxysulfonyl-1-naphthalenyl)methylene]-2,5-cyclohexadien-1-ylidene]-N-ethylethanaminium